Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$224.48	10.469%	$247.9808	$247.98	$248.00	$248.00
Purchase #2	$211.26	10.394%	$233.2184	$233.22	$233.20	$233.20
Purchase #3	$60.50	9.289%	$66.1198	$66.12	$66.10	$66.10
Purchase #4	$236.54	3.205%	$244.1211	$244.12	$244.10	$244.10
Purchase #5	$124.54	13.275%	$141.0727	$141.07	$141.05	$141.10
Purchase #6	$49.54	9.793%	$54.3915	$54.39	$54.40	$54.40
Purchase #7	$177.31	4.476%	$185.2464	$185.25	$185.25	$185.20
7 purchase totals =	$1,084.17		$1,172.1507	$1,172.15	$1,172.10	$1,172.10